Tropical & Subtropical Fruits

Degree of bienniality as related to yield potential and agro-climatic conditions

• There is a contention that the high yield potential in certain varieties may be a factor in causing higher degree of bienniality. The basis for this contention is that higher yield causes over-exhaustion of tree and conse¬quently the tree may not be able to restore its floriferous energy for cropping in the following year. This contention is, however, not tenable when yield data of different varieties and hybrids is considered. (Table-1a). A variety like Baneshan or a hybrid like Neeleshan have exhibited high yield potential but they are weakly biennial. Conversely, the varieties like Alphonso and Pairi have exhibited lower yield potential but they are strongly biennial.
• The mango is a tropical tree. As such, the varieties adapted to warm and dry regions have expressed higher yield potential with relatively lower degree of bienniality as seen in varieties of Andhra Pradesh as compared to those adapted to mild tropical rainy climate that exist in northern parts of Karnataka and Maharashtra varieties like Alphonso and Pairi. It is interesting to note that Cv. Khadar which is a warm-region adapted eco-type of Alphonso

(Rao et al., 1990 a: Rao et al., 1993) has been recorded as moderately biennial (Table-2) as compared to Alphonso.
Table 2: Comparative yield potential and degree of bienniality in syn­onym mango varieties — Alphonso and Khadar

Particulars	Cv. Alphonso	Cv. Khadar
7-year (1983-89) mean number of fruits per tree per year	437	425
Mean weight of fruit (g)	198	309
Estimated yield per ha (t)	5.9	8.9
Degree of bienniality (% deviation in year-to-year yield)	81.0	42.0